The present invention relates to an alloy having antibacterial effect and sterilizing effect, and a process for producing the same.
It is known that when oxides of titanium are irradiated with ultraviolet rays, the oxides exhibit antibacterial effect and hydrophilicity by their optical catalyst action. Antibacterial materials to which this principle is applied include a tile on which a thin TiO.sub.2 film is formed (Japanese Patent Application Laid-Open No. 8-66635). As metallic materials containing TiO.sub.2 and having optical catalyst function, there are developed antibacterial materials containing, as a matrix, titanium or titanium alloy (Japanese Patent Application Laid-Open No. 8-252461) or nickel or nickel alloy (Japanese Patent Application Laid-Open No. 10-18095). The Japanese Patent Application Laid-Open No. 8-252461 describes a method of pickling an titanium alloy containing 0-20% of a transition metal as an auxiliary component with an inorganic acid and heat-treating the alloy, thereby forming an oxide film on its surface. The Japanese Patent Application Laid-Open No. 10-18095 states that a composite metal plating-film in which titanium oxide is dispersed is formed on the surface of nickel or a nickel-chromium alloy, and this antibacterial material is effective in spots wherein unwanted bacteria propagate easily, such as a sink in kitchen equipment in a hospital institution or other institutions.
It is known that copper is a metal exhibiting sterilizing effect. Since early times, therefore, alloy containing copper has been used for coins, ornaments, tableware and the like. Copper exhibits its sterilizing effect when target bacteria contact the copper directly or the ion of the copper is produced in an aqueous solution.
As sterilizing metallic materials containing copper, the following are proposed: a Cu-containing stainless steel (Japanese Patent Application Laid-Open No. 8-229107), a stainless steel wherein the concentration of Cu is heightened in its surface layer, and a process for producing the same (Japanese Patent Application Laid-Open Nos. 8-60301, 8-60302 and 8-60303), a material having sterilizing effect by addition of Cu to a stainless steel, whereby prevention of infection, such as periodical sterilization, is unnecessary (Japanese Patent Application Laid-Open No. 9-170053) and the like. All of them are brought into direct contact with bacteria, to sterilize the bacteria.
Titanium and materials comprising as their main component titanium, among metallic materials having antibacterial effect based on optical catalyst function, belong to metallic materials which are relatively difficult to work. Nickel or nickel alloy wherein on its surface a composite metal plating-film in which titanium oxide is dispersed is formed has problems that a complicated plating step is necessary and that if the titanium oxide content in the plating layer increases, the adhesion of the plating onto the base metal decreases.
Furthermore, metallic materials having both antibacterial effect based on optical catalyst function and sterilizing effect cannot be found in the prior art. Metallic materials having only the sterilizing effect based on optical catalyst function do not exhibit any effect when they are not irradiated with light.